MainWP is a plugin which is intended to be installed in a copy of WordPress by itself. I’ve done that, and connected it to all of the sites I maintain by using the MainWP Child plugin. If you see that this plugin is installed in your copy of WordPress, then your copy of WordPress is being automatically updated, as are most if not all of your plugins.
As I’ve used this for a little while now, the behavior tends to be that I receive an e-mail with the list of sites and which updates have become available the first evening, and the updates that were available that evening get installed at some point during the next evening when the next check happens. Using this has eliminated a great many tedious tasks since the number of WordPress sites I need to keep updated has increased.
MainWP also has an iThemes Security extension which I have purchased. This makes keeping our blacklists and whitelists in sync with minimal effort as quickly as possible. I really just wanted a plugin that could do that simple thing, but finding one that also keeps every site on the latest version of everything is pretty awesome too.